The overall focus of this research program is to describe the effects of multichannel wide-dynamic range compression (WDRC) amplification on speech intelligibility. Hearing aids (and by extension, hearing rehabilitation programs) are now based on this technology, which is expected to improve speech intelligibility over conventional amplification strategies. At present it is unclear whether the inconsistent benefit from multichannel WDRC seen in previous studies was due to a failure of the hearing aid to preserve and transmit acoustic information, or to the listener's inability to process transmitted information. We hypothesize that changes in signal audibility and/or temporal cues can be described by measuring speech characteristics at the output of the amplification system and will partially account for differences in intelligibility across subjects. Few attempts have been made to understand the effects of hearing aids by actually measuring the acoustic characteristics of speech as transmitted to the listener (i.e., at the output of the hearing aid). Using recorded natural speech tokens measured at the output of the amplification system, we propose to identify specific acoustic cues (e.g., rise time, spectral peak) that are enhanced or disrupted by multichannel WDRC. Additionally, we intend to measure the extent to which these cues are altered by variations in compression parameters (release time, number of channels). We will relate changes in the acoustic signal to intelligibility. Finally, we will determine if the consequences of WDRC for speech intelligibility differ as a function of age and whether age-related performance differences, if they exist, are linked to the alteration of the temporal characteristics of the signal. [unreadable] [unreadable]